The battle at Lostwithiel occurred in two phases; an initial royalist assault on the high ground around Lostwithiel and then a pause marked by continual skirmishing before a final assault on the remnants of the parliamentarian army as it attempted to retreat beyond Lostwithiel toward Fowey in a vain attempt to be rescued or supported by sea. 

By 14 August 1644 the King had marshalled his forces to the north and west of Lostwithiel.  His own headquarters were at Lord Mohan’s house at Boconnoc, a little over 2.5 miles east of the town.    Prince Maurice’s army were also on that side of Lostwithiel and the royalists had posted units at Cliffe, Bodinnick and Polruan along the eastern bank of the river Fowey to guard the crossings there and control that waterway.  Sir Richard Granville had meanwhile taken Lanhydrock House as his headquarters, about 3 miles north of Lostiwthiel on the west side of the river Fowey.

According to Walker, following a Council of War on 18 August, the royalists determined to draw closer to Lostwithiel with the aim of either bringing the parliamentarians to battle or making their positions untenable. Both royalist and parliamentarian sources agree that this plan was put into execution early in the morning of 21 August when the Oxford army drew out in battle formation, infantry in the centre and cavalry on the flanks, onto heath land to the west of Boconnoc and then occupied Beacon Hill. Maurice’s army deployed similarly to the north of this position toward the high enclosed ground.  According to the royalist newspaper Mercurius Aulicus in the course of the day the King ‘fastened his army within enclosures on the wings of theirs within musket shot of each other’.  The earl of Essex’s account and Walker’s suggest respectively that this involved the capture of enclosures adjacent to Beacon Hill and on the high ground toward which Maurice’s soldiers had deployed that morning. 

It appears that at least some of these hedged fields had been defended by Essex’s regiments.  Symonds made clear that there was constant exchange of fire between Maurice’s men and the parliamentarians with the houses on the side of the hill where this action took place being set on fire by Essex’s units.  Mercurius Aulicus separately indicated that the parliamentarians had occupied the hedged fields to the west that ran toward the high ground taken by the royalists and a forlorn hope of 400 musketeers under Lieutenant Colonel Richard Ingoldsby had initially been positioned forward of the main deployment.  Essex himself said that Ingoldsby’s men were by Beacon Hill and it seems likely that they would have used the enclosures there as a defensive position from which they must have been ejected by the royalists.     

Whilst some fighting therefore appears to have taken place as the Oxford and Western armies advanced, further action occurred around Restormel castle.  Here Granville’s men, an advance party of 700 foot according to Symonds, quickly drove off Colonel Weare’s troops which had been positioned there to defend the castle and a nearby crossing of the Fowey.  However, Granville’s soldiers were counter-attacked in the afternoon by both parliamentarian horse and foot.  According to Symonds and Walker, this attack was thrown back by elements of Sir George Vaughan’s cavalry regiment.  As Vaughan’s command was part of the Oxford army it appears Granville’s force had been reinforced, possibly before his attack commenced given the relatively small numbers of cavalry at his disposal.   

To consolidate their position the royalists constructed overnight on 22 August a small redoubt on the top of Beacon Hill, ‘between our hedges and the enemy’s hedges’ according to Symonds, from where they could fire cannon on the parliamentary positions.  The next day artillery fire was exchanged between the opposing armies. 

The royalists planned to attack again on 24 August, but this was called off because, Walker said, it was clear the parliamentarians had been forewarned about the attack.  Instead , Lt General George Lord Goring was sent with around 2,000  royalist cavalry and 1,500 musketeers under Sir Thomas Bassett to St Blazey to block the bridge there over the river Par with the aim of closing the net further on Essex and  preventing his cavalry from grazing on the western side of the Par.  

This had the desired effect as, on 30 August, the parliamentarians decide that their cavalry needed to try and break out of the royalist cordon.  In the early hours of 31 August all of Essex’s cavalry, apart from the regiment of Plymouth horse, attempted to slip by the royalist armies on the Lostwithiel to Liskard road.  The royalists had been forewarned of this by parliamentarian deserters, but failed to intercept the fleeing cavalry.  With much of the royalist cavalry at St Blazey, part of the Earl of Cleveland’s brigade gave chase and forced a short action to the east of Boconnoc on Braddock Down (the site of  a civil war battle in 1643) , before the parliamentarians, who far outnumbered Cleveland, managed to escape. 

The breakout was accompanied by a decision by Essex to reduce his defensive perimeter around Lostiwthiel.  Without the horse he could no longer be certain of protecting his access to the sea and possible support from the fleet via the anchorages at  Minabilly and Polkerris; the harbour in the village of Fowey had ceased to be viable when the royalists captured the castle at Polruan, which dominated the mouth of the river  from the opposite bank, in mid-August.  

In pouring rain on the morning of 31 August, the second phase of the battle of Lostwithiel commenced.  The parliamentarian infantry, having blown up the church and plundered the town, began to withdraw via the roads which led into the hills to the west before turning toward the coast.  A rear party attempted to break down the bridge over the river Fowey, but was driven off by the royalists who quickly moved to pursue Essex’s men.   The heavy rain made the roads difficult and the parliamentarians lost five cannon to the mud as they retreated.  Walker indicated that Essex’s men drew up in battle formation in the fields beyond the town before continuing their withdrawal, suggesting it was made in good order.  But both royalist and parliamentarian sources reported a running fight developing from hedge to hedge over a distance of two to three miles between the parliamentarian rearguard and royalist forlorn, the latter apparently consisting of Granville’s Cornish soldiers. 

Eventually, having gained some high ground protected by enclosures, the parliamentarians turned to make a stand.  The earl of Essex indicated four foot regiments, his own, Major General Philip Skippon’s, Lord Robert’s and Colonel Barclay’s along with the Plymouth horse, which had been withdrawn from around St Blazey, formed this defensive line and forced back Granville’s men two or three fields, capturing three infantry and one cavalry colour and around 60 soldiers.  The royalist position was stabilised by an attack from the Queen’s troop of horse, which drove the parliamentarians back. 

At this point, around midday, the royalist advance halted to await the arrival of the rest of the army and an expected attack in the west across the river Par from St Blazey by Goring with the horse and Bassett’s infantry brigade, which, according to Walker, occurred at about 2pm.  Symonds reported further fighting between the foot for much of the afternoon as the parliamentarians continued their withdrawal, with the royalists steadily gaining ground. At around 4pm the Plymouth horse again attacked the royalist foot, but withdrew on the approach of the King’s Lifeguard of horse under Lord Bernard Stuart, allowing the royalist foot to advance once more.

Shortly after this action, Goring met-up with the King, possibly having fought his way across St Blazey bridge and defeated the parliamentarians defending the area around Tywardreath for which archaeological evidence has been found (see the section on archaeology).  The King ordered Goring to pursue the parliamentarian horse which had broken out earlier in the day, though if Symond’s is to be believed this did not happen immediately as Goring advised on the closing stages of the battle. 

The royalist push had taken them on to what Symond’s described as a high hill on a narrow passage of land between Tywardreath and the river Fowey.  Here the parliamentarians counterattacked again, driving back the royalist foot a couple of fields.  But the royalists stabilised their position once more and returned to the attack, driving back the parliamentarians.  Under this pressure, Colonel Weare and Essex’s own regiments refused to stand and opened up the parliamentarian right flank for the royalists to exploit, allowing them to get behind the position and threaten any further retreat to Fowey, Minabilly or Polkerris.  This, Walker said, forced the parliamentarians to withdraw to the ruins of an old castle; a reference to Castle Dore.  

Following a council of war which agreed the impracticality of trying to withdraw the parliamentarian army to the coast, early on the morning of 1 September Essex, Sir John Merrick, the General of the Ordnance, and Lord Roberts escaped by sea.   Major General Philip Skippon was left to treat and surrender terms were agreed later that day. These allowed for the parliamentarians to march away once the cannon and the arms and ammunition of the rank and file had been surrendered. Despite the articles of surrender allowing for a royalist cavalry guard, the parliamentarians were pillaged by the local people and royalist soldiers as they marched away;  of the 6,000 parliamentarian infantry that left Lostwithiel only 3,000 were said by Walker to have arrived in Poole.